7 research outputs found
A goal management intervention for polyarthritis patients: rationale and design of a randomized controlled trial
Gas-Phase Epoxidation of Propene with Hydrogen Peroxide Vapor
A study on the gas-phase epoxidation
of propene with vapor hydrogen peroxide has been carried out. The
main purpose was to understand the key factors in the reaction and
the relationship between epoxidation of propene and decomposition
of hydrogen peroxide, which is the main side reaction. The decomposition
was highly influenced by the materials used, being higher in metals
than in polytetrafluoroethylene (PTFE) and glass, and it was complete
when the epoxidation catalyst, TS-1, was introduced in the system.
However, when propene was added, the peroxide was preferentially used
for the epoxidation, even with amounts of catalyst as small as 10
mg, reaching productivities of 10.5 kg<sub>PO</sub>·kg<sub>cat</sub><sup>–1</sup>·h<sup>–1</sup> for a gas hourly
space velocity (GHSV) of 450 000 mL·g<sub>cat</sub><sup>–1</sup>·h<sup>–1</sup>. The hydrogen peroxide
was converted completely in all the experiments conducted, with a
selectivity to PO of around 40% for all peroxide concentrations. Finally,
if concentrations of propene higher than the stoichiometrically required
amounts were used, the selectivity to PO increased to almost 90%
Transfer of the Epoxidation of Soybean Oil from Batch to Flow Chemistry Guided by Cost and Environmental Issues
The simple transfer of established chemical production processes
from batch to flow chemistry does not automatically
result in more sustainable ones. Detailed process understanding
and the motivation to scrutinize known process conditions
are necessary factors for success. Although the focus is usually
“only” on intensifying transport phenomena to operate under
intrinsic kinetics, there is also a large intensification potential
in chemistry under harsh conditions and in the specific design
of flow processes. Such an understanding and proposed processes
are required at an early stage of process design because
decisions on the best-suited tools and parameters required to
convert green engineering concepts into practice—typically
with little chance of substantial changes later—are made
during this period. Herein, we present a holistic and interdisciplinary
process design approach that combines the concept of
novel process windows with process modeling, simulation, and
simplified cost and lifecycle assessment for the deliberate development
of a cost-competitive and environmentally sustainable
alternative to an existing production process for epoxidized
soybean oil
Water and n‑Heptane Volume Fractions in a Rotor-Stator Spinning Disc Reactor
This paper presents the volume fractions of n-heptane
and water
measured in a rotor-stator spinning disc reactor. The volume fractions
were measured using γ-ray tomography and photographic image
analysis. The volume fractions were determined as a function of rotational
disc speed, flow ratio, position in the reactor, and rotor material.
In addition, the effect of the density difference between water and
n-heptane was determined by dissolving potassium iodide in the water
phase. Below a rotational disc speed of 75 rpm the volume fraction
measured by tomography and photographic image analysis are within
10% deviation. For low rotational disc speeds, the n-heptane volume
fraction decreases slightly with increasing rotational disc speed:
the centrifugal force accelerates the larger n-heptane droplets to
the center. At higher rotational disc speeds the droplets become smaller
accordingly, the friction between the phases determines the flow,
and the n-heptane volume fraction becomes equal to the n-heptane to
total flow ratio. An increase in density difference from 0.31 to 0.79
kg dm<sup>–3</sup> did not influence the volume fractions
Design of a thick-walled screen for flow equalization in microstructured reactors
A systematic computational fluid dynamics (CFD) approach has been applied to design the geometry of the channels of a three-dimensional (thick-walled) screen comprising upstream and downstream sets of elongated channels positioned at an angle of 90° with respect to each other. Such a geometry of the thick-wall screen can effectively drop the ratio of the maximum flow velocity to mean flow velocity below 1.005 in a downstream microstructured reactor at low Reynolds numbers. In this approach the problem of flow equalization reduces to that of flow equalization in the first and second downstream channels of the thick-walled screen. In turn, this requires flow equalization in the corresponding cross-sections of the upstream channels. The validity of the proposed design method was assessed through a case study. The effect of different design parameters on the flow non-uniformity in the downstream channels has been established. The design equation is proposed to calculate the optimum values of the screen parameters. The CFD results on flow distribution were experimentally validated by Laser Doppler Anemometry measurements in the range of Reynolds numbers from 6 to 113. The measured flow non-uniformity in the separate reactor channels was below 2%